As a Global Positioning System (GPS) technology advances, and GPS receivers are used as location sensors in commercial vehicle navigation systems. Also, a location-based service (LBS) such as a road guidance service and a location-based information providing service is provided based on location information of the vehicle obtained by the GPS receiver. Moreover, a location-based control by using the GPS is performed in a military vehicle and guided arms. However, since the GPS receiver cannot completely or partially receive GPS satellite signals in a tunnel, an underground parking lot, a downtown area and a mountain area, location information cannot be continuously provided to the user.
Therefore, in order to provide the continuous location information regardless of the places, an Inertial Navigation System (INS)/GPS integrated navigation system integrating a GPS receiver with the INS employing an inertial sensor, e.g., an accelerometer and a gyroscope, is proposed. The INS/GPS integrated navigation system is generally used in military systems, but there is a limitation in using it for general commercial purposes because it is an expensive navigation system. To resolve this problem, researchers are studying to develop an inexpensive INS/GPS integrated navigation system.
The INS/GPS integrated navigation system can be designed in various forms based on the type of the INS and the kind of an integration filter. A Kalman filter is used as the integration filter. Since the INS has a nonlinear function, an extended Kalman filter (EKF) is mainly used.
The EKF can estimate an error precisely when an initial error and disturbing noise are small and there is no uncertainty in a model. Since the above conditions cannot be always satisfied in the INS/GPS, there is a shortcoming that error does not converge.
In order to complement the shortcoming of the EKF, researchers are studying various filters such as a sigma point Kalman filter (SPKF), a receding horizon Kalman finite impulse response (RHKF) filter, and an interacting multiple model (IMM). However, an infinite impulse response (IIR) type filter and a finite impulse response (FIR) type filter have mutually complementing characteristics. Thus, when one of the filters is used, the advantage of the other filter cannot be taken. Therefore, a navigation system employing the EKF having IIR characteristics, which is not robust in various error environments, has a problem that errors may occur whenever a error environment is given.